#include <stdio.h>

int main()
{
    double salary, rate;
    scanf("%lf", &salary);
    if (salary <= 1600)
    {
        printf("0.00");
    }
    else
    {
        if (salary <= 1600)
        {
            rate = 0.0;
        }
        else if (salary <= 2500)
        {
            rate = 0.05;
        }
        else if (salary <= 3500)
        {
            rate = 0.1;
        }
        else if (salary <= 4500)
        {
            rate = 0.15;
        }
        else
        {
            rate = 0.2;
        }
        printf("%.2f", rate * (salary - 1600));
    }

    return 0;
}